COUROUPITA GUIANENSIS LEAF CALLUS EXTRACT MEDIATED SYNTHESIS AND ANTIBACTERIAL ACTIVITY OF SILVER NANOPARTICLES.

Objective: Synthesis of varied sized and morphologically distinct silver nanoparticles (AgNPs) using callus/callus extract, and their promising antibacterial and cytotoxicity was reported from very few plant systems. Here, we investigated silver nanoparticle synthetic potential of Couroupita guianensis leaf callus extract and their antibacterial activity.Methods: synthesis of callus mediated silver nanoparticles and characterisation of physical, chemical, and antibacterial activity of AgNPs.Results: Callus extract rapidly reduced silver ions and stabilized nanoparticles have displayed characteristic maximum UV absorbance at 410 nm. SEM and AFM images revealed their spherical morphology and size variation, which is ranged from 30.38 nm to 88.32 nm and were in small aggregates. Capping of AgNPs by the phenolic compounds and proteins revealed from FTIR spectral peaks. Silver nanoparticles displayed significantly high antimicrobial activity against both Gram positive and negative bacterial strains compared to silver ions and gentamicin. This enhanced antimicrobial activity of AgNPs may due their small size leading to efficient molecular contact with cell surface, and uptake and interaction with vital biomolecules.Conclusions: Stable AgNPs were synthesized through reduction and capping of silver ions by polyphenols and proteins present in callus extract. Theenhanced antimicrobial activity of AgNPs may due to their small size leading to efficient molecular contact with the cell surface, penetration, andinteraction, and inactivation of vital biomolecules.Â

A conceptual sediment transport model for arid regions

A conceptual model of an instantaneous unit sediment graph (IUSG) has been developed for sediment transport prediction in the arid regions. It involved routing of the sediment through a cascade of identical linear reservoirs. The sediment graphs generated by convolution of IUSG compared well with the observed values for four representative arid sub-basins of the Luni River in India. The sediment supply is related to the effective precipitation and to transmission losses in the upland and channel phases, respectively, and the model parameters are estimated from the observed events. The model can be applied to ungauged flow events through parameterization. (C) 1996 Academic Press Limite

HYDROLOGIC ROUTING OF FLOW IN ARID EPHEMERAL CHANNELS

Hydrographs of ephemeral streams in an arid region usually decrease significantly in magnitude, downstream I unless they are augmented by tributary flows. Estimation of outflow hydrographs from a channel reach is essential for the development of water-resources systems. A hydrologic-flow-routing technique for arid ephemeral channels is developed. The hydrologic-routing equations for the movement of flood waves are modified by the inclusion of a nonlinear volumetric transmission loss rate term, which is empirically estimated from the observed inflow-outflow data for a channel reach. The predicted outflow hydrographs match better with the observed than the outflow hydrographs generated through the lumped regression model for ephemeral channels. The hydrologic-flow-routing technique may also be used for ungaged channel reaches through parameterization

Ephemeral flow modelling in arid regions

Flow hydrographs in arid upland basins, where the runoff is directly related to the rainfall, are simulated by a combination of regression and differential equation techniques. The rising limb of the hydrograph is modelled through a regression analysis and the recession portion through a conceptual analog of discharge from a single leaky reservoir, which is described by a continuity equation and by discharge-stage and storage-stage relations at the basin outlet. A good agreement between observed and model-predicted recession curves was obtained by optimizing the reservoir leakage rate and the initial storage in the reservoir. Best parameter values are physically realistic and best reservoir configuration has leakage that varies as the cube of stage for the initial event of the season in the organised stream network and as the square of the stage for rest of the events. The technique can be applied to the ungauged flow events through parameterization. (C) 1996 Academic Press Limite

ESTIMATING TRANSMISSION LOSSES IN AN ARID REGION

Flow volumes in ephemeral streams in and regions decrease significantly in magnitude downstream. These transmission losses are important not only in their obvious effect on flow reduction, but also as a source of groundwater recharge to underlying alluvial aquifers. A distributed model for estimation of transmission losses described herein represents an attempt to develop a procedure for practical applications and is shown to produce reasonable estimates. The model is simplified and requires a minimum of observed data for calibration. Based on available information obtained from Landsat Thematic Mapper False Colour Composites of bands 2, 3 and 4, published sources and regression analyses, the model can be used to estimate transmission losses from ungauged channels in arid regions. Transmission loss data are compared with some previously published data, and despite some scatter are generally consistent with them

Uniform and critical flow computations

The application of theory developed for direct integration of gradually varied flow equations to uniform and critical flow computation greatly reduces the computational effort. A small generalized subroutine is able to compute accurately the various parameters involved in the computation for all types of natural and constructed cross sections. Although the equations are implicit, in a majority of cases the number of iterations needed to achieve the required accuracy is less than 3. The method is even useful for computation by hand held calculators

Development of hydrologically optimal land formation practice for gully erosion susceptible ustifluvent soil

Creating conditions to induce maximum infiltration and minimum soil particle loaded runoff is the basic principle of water management for rainfed farming on erosion susceptible soil. The objective of this study was to develop a voluntarily adoptable practice that fulfils these conditions. Factors involved in plot infiltration and soil loss were analysed to form groups of indices to evaluate conditions of infiltration and soil loss. Field experiments were carried out in ustifluvent soil on a specially created erosion susceptible set of runoff plots of variable sizes (constant width and increasing lengths) and constant area with variable shapes (LIB ratio of 1, 4 and 16). Infiltration and soil loss data for individual rainstorm and accumulated yearly values established that a land formation of 18 m length for broad land form and a 0.9 m wide strip as secondary operation induced maximum infiltration and minimum soil loss. The land formation is related to agricultural practice so as to avoid runoff accumulation and maintain overland flow in bare as well as planted fields. This practice has been demonstrated to be voluntarily adoptable and can be performed with ordinary tractor and some minor equipment. Such land formation supports water conservation and minimises rill and gully formation. The danger of water logging or excessive erosion due to breaching that may occur as a result of excessively intense rainfall is also reduced. (C) 2002